Next-generation wireless communication systems consider employing wireless communication systems that use high-frequency bands, such as millimeter Waves (mmW), in order to support high-capacity data services. In a case of a system using high-frequency bands, a Base Station (BS) has a small cell radius due to the short communication distance between a BS and a Mobile Station (MS), and an increasing number of BSs are installed to secure the service area of the MS). The small cell radius of the BS and the increase in the number of BSs may cause an increase in the number of handovers of the MS) due to inter-cell movement of the MS). As a result, the amount of occurring signaling and consumption of system resources increase significantly.
The increase in the number of BSs increases requirements for the processing capacity of an access gateway that is connected to the BS to transfer data to the BS and manage service information and authentication information for users. Consequently, in a small-cell environment, a centralized network architecture is difficult to apply.
In a small-cell-based wireless communication system, a network architecture is needed which increases a data transmission speed while reducing the overload of the system due to frequent handovers. To solve problems caused by a small-cell architecture, a decentralized flat network architecture has been considered. Therefore, there is a need for providing functions such as a new handover scheme for supporting the mobility of the MS), a user policy and charging control scheme, and a Quality of Service (QoS) providing scheme in a decentralized flat network.